I have learned by using the “find”, “wc” and “awk” commands one can find the total number of lines within files of a given directory and sub-directories. Thanks to NicM on IRC server Freenode channel #OpenBSD for his solution below.

Solution
find /path/blah -type f -name ‘*.php’|while read i; do wc -l <$i; done|awk ‘BEGIN { x=0 }; { x+=$1 }; END { print x }’

Note: Shell must be bourne-compatible.